Help: cannot find vertex_normal as attribute in 2.93 beta
An alternative setup is suggested in the first (pinned) comment of the video.
TLDR : You can use normal instead of point_normal although it may be inaccurate. If you want an accurate result you can read through the rest of the answer.
Quotes from user Erindale :

A note on vertex_normal attribute: This has been removed as it as a
bit of a misnomer (although very useful). The method you'll need to
use now is to take normal attribute (this is the face normals) with an
Attribute Convert node (set to point (writes to point domain) and
vector (normal is a vector)) and then use an Attribute Vector Math
node set to Normalise to ensure those vectors all have length 1. I
recommend people make a reusable node group that handles this as it is
a pretty common thing to want. Here is an example of what that could
look like

From the twitter post :
https://twitter.com/erindale_xyz/status/1374764284811612161/


As a follow up, you can just use normal as an attribute instead of
vertex_normal and it will automatically convert to point domain if
it's used with another point domain attribute (eg position). There
will however been some inaccuracies without normalising. For effects
like this you may well get away with it unnoticed but with more uneven
geometry you may find that normalising is required. I just have a
group so that's what I recommend